To finance the deal, Verizon would have to launch one of the biggest bond offerings ever.

Citigroup earlier this year speculated Verizon could raise somewhere between $55 billion and $75 billion in debt. Barclays put it around $50 billion too. (The remaining amounts would, in varying scenarios, be made up of new equity and cash.)

Since May, the cost of issuing debt has shot higher thanks to the Fed Chairman’s warnings about pulling back on his bond-buying program.

By historical standards rates still remain low, but with many economists expecting the Fed to announce its tapering plans at its September meeting, Verizon may well see its window of opportunity closing.

Each increase in interest rates would cost Verizon dearly in such a giant deal.

Craig Moffett, senior research analyst at Moffett Research told WSJ tonight if the deal were to require roughly $60 billion of debt, each percentage point increase could potentially add some $600 million a year in interest costs to the deal’s price tag. “With interest rates rising, there has to be some sense of urgency that is now or never,” he said.

This round of talks, Verizon may want to keep its partner on the line until they’ve got a deal.